title: The role of IL-6 in the radiation response of prostate cancer.
abstract: BACKGROUND
  Hormone-resistant (HR) prostate cancers are highly aggressive and respond poorly to treatment. IL-6/STAT3 signaling has been identified to link with the transition of HR and aggressive tumor behavior. The role of IL-6 in the radiation response of prostate cancer was investigated in the present study.
  
  
  METHODS
  The murine prostate cancer cell line (TRAMP-C1) and the hormone-resistant cell sub-line, TRAMP-HR, were used to assess the radiation response using in vitro clonogenic assays and tumor growth delay in vivo. Biological changes following irradiation were investigated by means of experimental manipulation of IL-6 signaling. Correlations among IL-6 levels, tumor regrowth, angiogenesis and myeloid-derived suppressor cell (MDSC) recruitment were examined in an animal model.
  
  
  RESULTS
  HR prostate cancer cells had a higher expression of IL-6 and more activated STAT3, compared to TRAMP-C1 cells. HR prostate cancer cells had a greater capacity to scavenge reactive oxygen species, suffered less apoptosis, and subsequently were more likely to survive after irradiation. Moreover, IL-6 expression was positively linked to irradiation and radiation resistance. IL-6 inhibition enhanced the radiation sensitivity of prostate cancer, which was associated with increased p53, RT-induced ROS and oxidative DNA damage. Furthermore, when mice were irradiated with a sub-lethal dose, inhibition of IL-6 protein expression attenuated angiogenesis, MDSC recruitment, and decreased tumor regrowth.
  
  
  CONCLUSIONS
  These data demonstrate that IL-6 is important in the biological sequelae following irradiation. Therefore, treatment with concurrent IL-6 inhibition is a potential therapeutic strategy for increasing the radiation response of prostate cancer.
authors.affiliation: Department of Urology, Chang Gung Memorial Hospital, Keelung, Taiwan. wucgmh@gmail.com
authors.forename: Chun-Te
authors.initials: CT
authors.lastname: Wu
authors.forename: Miao-Fen
authors.initials: MF
authors.lastname: Chen
authors.forename: Wen-Cheng
authors.initials: WC
authors.lastname: Chen
authors.forename: Ching-Chuan
authors.initials: CC
authors.lastname: Hsieh
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000528:radiation effects; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D015151:Immunoblotting; D007150:Immunohistochemistry; D015850:Interleukin-6 / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000532:radiotherapy*; D011836:Radiation Tolerance / Q000502:physiology*
chemical_list: D015850:Interleukin-6